The tourmaline mineral group is chemically one of the most complicated groups of.
silicate minerals .
Tourmaline has a variety of colors. Iron-rich tourmalines are usually
black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow
Opaque black schorl and yellow tsilaisite are idiochromatic tourmaline species that have high magnetic susceptibilities due to high concentrations of iron and manganese respectively
Tourmaline was sometimes called the "Ceylonese
Sri Lankan Magnet" because it could attract and then repel hot ashes due to its
pyroelectric properties.
[2][4] Tourmalines were used by chemists in the 19th century to polarize light by shining rays onto a cut and polished surface of the gem
A crystal of tourmaline is built up of units consisting of a
six-member silica ring that binds above to a large
cation,such as sodium.
INTERESTING -
BMK - has chloites - ( salts ) lots of green colored ores - perhaps chlorite or, just maybe, green Tourmaline gem sort - but... there's another element involved - iron - which when in the presnce
of salts and carbecous ores - alkais - iron will oxidize - now lets examine this core pic...
1 - i see brown iron oxide in broken ores - near top
2 - i see solid black crystal - almost - tourmaline - inside f broken core - 4th down from top
3 - i see what seems to appear as - carbon jet black fines - extreme lower right - which could
indicate - carebon black presense -
4 - salts decasy iron - some turns brown - other ores turn carbon black powder - and some
may have transistioned to a salt crystal black = tourmaline gem.
ZOOM IN ON THIS BMK CORE PIC - what do you see ? https://macdonaldmines.com/wp-content/uploads/2021/02/IMG_5702-scaled.jpg Again... not all of BMK's ore are black.. .but some are.
TOURMALINE - WIKIPEDIA https://en.wikipedia.org/wiki/Tourmaline
EXAMPLE OF BLACK TOURMALINE - ( do i see gold in this specimine ? )
https://www.etsy.com/ca/listing/915554703/aaa-quality-black-tourmaline-rough?ref=pla_similar_listings_top_ad-4&plkey=23e67fe75d47f2bd8022f3acb63f74f71350269e%3A915554703&pro=1 YEAH... BMK, should check for carbon black fines...
And... Tourmaline gems... Hey.. .one never knows.
HIGH GRADE GOLD - ARE THESE THE JOVAN - SNEAK PEEKS ?
VERY NICE... 
Cheers....
P.S. why is this stock being held down ?
What's with the ask wall ?
Hmmm....